A) FIELD OF THE INVENTION
The present invention relates to a torsional vibration dampening apparatus and a lock-up device for a torque converter. More particularly, the torsional vibrational dampening apparatus includes inter-fitting fluid chamber portions having a slider therein which creates fluid flow resistance in response to displacement of relatively rotatable associated portions.
B) DESCRIPTION OF THE RELATED ART
Torque converters usually include a fluid coupling mechanism for transmitting torque between the crankshaft of an engine and the input shaft of an automatic transmission. In recent years, to improve fuel efficiency, some torque converters have included a lock-up devices that, upon reaching predetermined operating conditions, lock-up the torque converter so that power from the crankshaft of an engine is directly transmitted to the automatic transmission, bypassing the fluid coupling device. Upon engagement, lock-up devices often cause a shudder, or vibration. Further, while engaged, the lock-up device is subject to vibrations caused by sudden acceleration, or deceleration, or other vibration inducing circumstances associated with internal combustion engines. Consequently, torsional vibration dampening apparatus' are typically employed in lock-up mechanisms to dampen vibration.
One torsional vibration dampening apparatus employed in a lock-up device in the torque converter includes a fluid chamber which has an opening extending in circular directions and which is filled with viscous fluid. A slider member is disposed within the fluid chamber, divides the fluid chamber in circular directions into separate cells and is relatively movable in circular directions within the fluid chamber. The slider member is in contact with a rotary member coupled to the input shaft of the transmission and moves with the rotary member. A seal is provided to seal the opening. Relative movement by the slider within the chamber causes viscous fluid to flow through a clearance gap (choke) between the inner surfaces of the chamber and the outer surfaces of the slider from one cell of the chamber toward the other to produce viscous resistance. The seal element comes in press contact with other elements disposed outside the case to seal the opening of the fluid chamber. Since the seal element is placed outside the fluid chamber, however, it tends to deform. Deformation of the seal causes leakage of the viscous fluid from the fluid chamber, and as a result, a desirable level of viscous resistance cannot be obtained.